title: CT-based patient-specific modeling of glenoid rim defects: a feasibility study.
abstract: OBJECTIVE
  Reconstruction of glenoid bone defects requires accurate preoperative planning. The purpose of this study is to present a method for quantifying the defect size and generating a 3D model of the bone graft for augmentation by matching the fractured glenoid with the contralateral side.
  
  
  METHODS
  Ten paired shoulders from five cadavers (subjects: three women and two men; mean age, 85 years) and 60 paired shoulders in 30 patients (controls: nine women and 21 men; mean age, 21 years) were examined using CT to determine bilateral comparability by assessment of the maximum glenoid diameters, surface area, and volume. After creation of a glenoid rim defect in the study group, repeated CT scans were superimposed with the data from the contralateral side. The defect size was quantified and the missing fragment virtually reconstructed. Accuracy was evaluated by comparing the virtually repaired glenoid with the predefect CT scan.
  
  
  RESULTS
  There were no significant side-to-side differences in intact shoulders (p < 0.05). After creation of the glenoid defects, there was a mean decrease of 31% in the anteroposterior diameter, 34% in surface area, and 19% in volume. The virtually reconstructed glenoids did not differ significantly from the predefect CT scans. The averaged predefect-to-postdefect difference was 3% for the anteroposterior diameter (R(2) = 0.71), 6% for the surface area (R(2) = 0.82), and 4% for the volume (R(2) = 0.98).
  
  
  CONCLUSIONS
  A precise 3D model of the glenoid bony defect can be generated. The computer simulation provides a virtual model of the bone graft, which may potentially improve arthroscopic bone augmentation.
authors.affiliation: Department of Radiology, Charité-Universitätsmedizin Berlin, Charité Campus Mitte, Chariteplatz 1, Berlin, Germany 10117. gerd.diederichs@charite.de
authors.forename: Gerd
authors.initials: G
authors.lastname: Diederichs
authors.forename: Heiko
authors.initials: H
authors.lastname: Seim
authors.forename: Henning
authors.initials: H
authors.lastname: Meyer
authors.forename: Ahi S
authors.initials: AS
authors.lastname: Issever
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
authors.forename: Ralf J
authors.initials: RJ
authors.lastname: Schröder
authors.forename: Markus
authors.initials: M
authors.lastname: Scheibel
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D000465:Algorithms; D002102:Cadaver; D003198:Computer Simulation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008954:Models, Biological; D015233:Models, Statistical; D010363:Pattern Recognition, Automated / Q000379:methods*; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012784:Shoulder Fractures / Q000000981:diagnostic imaging* / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods*